How to Test Power Supply (SMPS)?

Power Supply is the most important part of your computer System because you can not work until your computer is not powering on.  Here I am describing some techniques that you can use to troubleshoot and overcome the SMPS Problems.

Functions Performed

Following Functions are provided by the SMPS (Switch Mode Power Supply):
Its main function is to provide required DC voltage to operate all components in the system.
Different Voltage levels obtained from same power supply.
Output is not affected by the input means if input voltage is between 120V AC to 240V AC the output obtained will be constant. It also provides electrical protection to all components from under voltage or over voltage.
It Provides Necessary Cooling to its components and protects computer from overheating. 

Voltage Levels
If you want to test SMPS than you should know voltage level on every pin of the connector so that testing can be performed:

24 PIN ATX Connector
SIDE A			SIDE B
Pin No.	Color	Voltage Level	Pin No.	Color	Voltage Level
1	Orange	+3.3 Volts	13	Orange	+3.3 Volts
2	Orange	+3.3 Volts	14	Blue	-12 Volts
3	Black	Ground	15	Black	Ground
4	Red	+5 Volts	16	Green	PS_ON
5	Black	Ground	17	Black	Ground
6	Red	+5 Volts	18	Black	Ground
7	Black	Ground	19	Black	Ground
8	Grey	Power good	20	White	NC
9	Purple	VSB  +5V	21	Red	+5 Volts
10	Yellow	+12 Volts	22	Red	+5 Volts
11	Yellow	+12 Volts	23	Red	+5 Volts
12	Orange	+3.3 Volts	24	Black	Ground

 Fig Given Below illustrates these pins on Connector

8 Bit Industry Standard Architecture(ISA) or PC Bus

ISA (Industry Standard Architecture) was first used with the IBM PC in 1981. It was the first open system for PC architecture. No restriction was put on the use of this interconnection method by the IBM. IBM offered free licensing of this PC architecture technique which resulted in more popularity of this. Some main features of 8 bit ISA are:

1) It was introduced by IBM and was the first open system for PC architecture.
2) It provides data transfer rate up to 4.77 Mbps.
3) ISA interface contains 62 pins to interface add on cards. These 62 pins are arranged in two rows, each containing 31 pins.
4) Distance between each pin is 0.1 Inches.
5) 8 Bit ISA make use of Following signals:
    3 Ground Signals
    2 +5V DC Supply
   +12,12,-5V DC supply
    Bidirectional 8 bit data Bus.
   20 Address line, hence memory address space of 1MB (2²⁰=1MB)
   3 DMA request lines
   3 DMA acknowledge lines.
   Six Interrupt Support

Table given below illustrates all signals used by this connector along with their functions: